1. Technical Field
This disclosure relates to an inkjet recording apparatus, and more specifically to an inkjet recording apparatus used as, for example, a copier, a printer, a facsimile machine, or a multi-functional device having two or more of the foregoing capabilities.
2. Description of the Related Art
Conventionally, non-impact recording methods are known to be advantageous in that noise is negligibly small during recording. Of the non-impact recording methods, in particular, inkjet recording methods are quite useful because they allows high-speed printing without any special fixing process on a plain sheet of paper. Recently, in the field of the inkjet recording method, a large number of color recording methods using color inks have been proposed and improved.
As one of such inkjet recording methods, an inkjet recording method is proposed to fly ink droplets of different colors and attach the droplets on a recording medium for recording. An inkjet recording apparatus employing the inkjet recording method has an inkjet head above the recording medium horizontally conveyed to eject ink droplets toward just below the inkjet head and a carriage to reciprocally move the inkjet head in a width direction relative to the recording medium.
The inkjet recording apparatus also has an ink receiving assembly at an external area in a width direction of a printing area at which printing is performed on the recording medium, that is, outside the printing area. The ink receiving assembly has a porous sheet horizontally disposed opposing nozzles of the inkjet head and a collection tank disposed below the porous sheet.
During activation of the inkjet recording apparatus, ink droplets for dummy ejection not contributing to recording are regularly ejected from the nozzles to the ink receiving assembly to prevent ejection failure caused by an increase in the viscosity of ink adhering on nozzles during non use. As the dummy ejection, for example, ink droplets may be ejected a few tens of times per nozzle every a few seconds. The dummy ejection may be performed at the start of printing or after cleaning operation to prevent different color inks to mix each other.
The dummy ejection allows removal of viscosity-increased ink adhering on nozzles, thus preventing such viscosity-increased ink from drying and clogging the nozzles. For the above-described ink receiving assembly, since ink droplets are ejected vertically downward, i.e., the same direction as the gravitational direction, the ink droplets land on the porous sheet while maintaining a high speed, thus preventing the ink droplets from turning into mist.
By contrast, inkjet recording apparatuses are becoming widely used that vertically convey recording media and have an inkjet head to eject ink horizontally, not vertically downward, from nozzles. If such an inkjet recording apparatus employs an ink receiving assembly including a horizontal porous sheet as described above, the distance at which ink droplets for dummy ejection fly from when the ink droplets are horizontally ejected nozzles to when the ink droplets drop on the horizontal porous sheet is longer than that of the above-described configuration in which ink droplets are ejected vertically downward from nozzles. As a result, the ink droplets ejected from the nozzles may speed down, turn into ink mist, and spread around.
In other words, when ink droplets fly a long distance, the ink droplets suspend due to air resistance and turn into mist. Such ink mist spread around to the nozzle face of the inkjet head and is scattered inside the apparatus by internal turbulence caused by the reciprocal movement of the carriage. As a result, the inside of the inkjet recording apparatus may be contaminated with ink mist.
To deal with such a failure, ink droplets need to land on the ink receiving assembly before turning into mist Hence, for example, as illustrated in FIG. 1, an ink receiving assembly 102 is proposed in which a porous sheet 101 is vertically disposed opposing nozzles 100 (see, for example, JP-3707274-B1 (JP-2000-153621-A)).
The ink receiving assembly 102 has a case 105 and the porous sheet 101. The case 105 includes a first cylindrical body 103 and a second cylindrical body 104. The first cylindrical body 103 is connected to the second cylindrical body 104 so as to form an angle of 130 degrees relative to the second cylindrical body 104 at a middle portion of the case 105. The porous sheet 101 is rectangular and mounted on an opening portion 105a of the case 105. The periphery of the porous sheet 101 is surrounded by and fixed at the opening portion 105a of the case 105.
For the ink receiving assembly 102, ink droplets 106 horizontally ejected from the nozzles 100 for dummy ejection are absorbed into the porous sheet 101 and, as indicated by arrows in FIG. 1, flow downward inside the porous sheet 101 and drop from a lower end of the porous sheet 101. Furthermore, the dropped ink moves inside the case 105 and is collected to a collection tank.
In addition, for example, an ink receiving assembly is proposed that has a driving pulley, a driven pulley disposed at a position horizontal to the driving pulley, a belt horizontally looped around the driving pulley and the driven pulley, and a collection tank having an edge portion in contact with a lower side of the belt (see, for example, JP-2001-162836-A).
For the ink receiving assembly, ink droplets for dummy ejection are ejected vertically downward from an inkjet head and adhere on an upper face of the belt just below the inkjet head. When the ink droplets accumulate on the upper face of the belt, a driving roller is rotated to move the ink droplets with the belt. The ink droplets move around to the lower side of the belt, are scraped by the edge portion of the collection tank, and are collected into the collection tank.
However, for the ink receiving assembly 102 in which the porous sheet 101 is vertically disposed, ink droplets 106 ejected for dummy ejection are absorbed into the porous sheet 101. As a result, a portion of ink droplets 106 passes through the porous sheet 101 and turns into mist, thus contaminating the inside of the inkjet recording apparatus. In addition, since the porous sheet 101 is vertically disposed, a portion of the ink droplets 106 absorbed may remain at the lower end of the porous sheet 101 without dropping from the lower end, thus increasing the viscosity and hardening. As a result, hardened ink may reduce the effect of preventing occurrence of mist, reduce the absorbing performance of the porous sheet 101, and hamper smooth dropping from the lower end of the porous sheet 101.
For the ink receiving assembly having a belt horizontally disposed to receive ink droplets ejected for dummy ejection, ink droplets adhering on the belt are scraped by the edge portion of the collection tank disposed at the lower side of the belt. As a result, ink droplets ejected for dummy ejection and adhering on the belt are not scraped until the ink droplets moves to the lower side of the belt. As a result, ink may adhere on a wider area and drop from the edges of the belt, or ink may evaporate and firmly fix. In addition, when the belt of the ink receiving assembly is vertically disposed to apply the ink receiving assembly to an inkjet head that horizontally ejects ink droplets for dummy ejection, the above-described failure may arise.